[j-nsp] MPLS VPN Load-balancing

[Steven Brenchley]

Hi Christian,
     The problem your hitting is a limitation of the M10i chip set.  It can
only look at the top two labels and since both top labels are the same for
all this traffic it's going to look like the same flow and send it all
across the same link.  The only way I've been able to get a simulance of
load balancing is by creating multiple LSP's between the same end points and
manually push different traffic across the different LSP's.  It's really
clunky but there are no switches that will work around this limitation on
the current M10i CFEB.
      If you where using a T-series, M320,M120, or MX router you don't have
this limitation.  They can all go deeper into the packet to determine load
balance.
      On the a semi brighter side, on the horizon there are some new Ichip
based CFEB's which will not have this limitation.  I don't recall when those
will be available but you could probably get a hold of your SE and get a
time table from them.

Steven Brenchley

===============================

On Tue, Aug 11, 2009 at 3:16 PM, Christian Martin <
christian.martin at teliris.com> wrote:

> NSP-ers,
>
> I have a Cisco---Juniper pair connected over a pair of T3 links.  The
> Juniper acts as a PE and is pushing two labels for a specific route learned
> on the PE destined to a single remote PE well beyond the Cisco P.  The
> traffic is destined to several IP addresses clustered in this subnet (sort
> of like 10, 11, 12, 13) and the forwarding table shows that there are two
> correctly installed next-hops - same VPN label, different LDP label (we have
> applied several different types of hashings and of course have our
> forwarding table export policy in place).  Nevertheless, the Juniper is
> doing a very poor job load-balancing the traffic, and the Cisco is splitting
> it almost evenly.  There is in fact a larger number of routes being shared
> across this link (about 20 or so VPN routes in different VRFs and thus
> different VPN labels – all sharing the same 2 LDP labels, but one particular
> subnet pair is exchanging quite a bit of traffic).  All of the addresses are
> unique within our domain.
>
> Has anyone had issues with load-balancing a single subnet across an MPLS
> VPN link pair?  Note again that this is a PE-P (J--C) problem and that the
> IP addresses are all arranged locally.  I know Juniper are secretive about
> their hashing algorithm (can't lose any hero tests, can we?), but we are
> getting like 5:1 load share if we are lucky and are bumping up against the
> T3's capacity.  The box is an M10i.
>
> As always, any help would be appreciated.
>
> Cheers,
> C
>
> show route forwarding-table destination 10.160.2.0/24
>
> Routing table: foo.inet
> Internet:
> Destination        Type RtRef Next hop           Type Index NhRef Netif
> 10.160.2.0/24      user     0                    indr 262175     2
>                                                 ulst 262196     2
>                                                Push 74   600     1
> t3-0/0/0.1000
>                                                Push 74   632     1
> t3-0/0/1.1000
>
>
> PE-P next-hop count (all showing load-balancing in effect)
>
> show route next-hop 172.16.255.11 terse | match > | count
> Count: 106 lines
>
>
> monitor interface traffic
>
> Interface    Link     Input bytes        (bps)      Output bytes
>  (bps)
>  t3-0/0/0      Up    541252651233   (25667208)      691166913860
> (35611752)
>  t3-0/0/1      Up    279149587856    (8737568)       24893605598
>  (20112)
>
>
> Note that the Cisco is doing 25/9 Mbps and the Juniper 35/.02.
>
>
>
>
>
>
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
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>



-- 
Steven Brenchley
-------------------------------------
There are 10 types of people in the world those who understand binary and
those who don't.